Preparation method of liquid bis (fluorosulfonyl) imide alkali metal salt

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a preparation method of liquid bis (fluorosulfonyl) imide alkali metal salt. The preparation method of the liquid bis (fluorosulfonyl) imide alkali metal salt provided by the invention comprises the following steps: 1) reacting bis (fluorosulfonyl) imide with an alkali metal source in a poor solvent of the bis (fluorosulfonyl) imide alkali metal salt, and carrying out first solid-liquid separation to obtain a bis (fluorosulfonyl) imide alkali metal salt crude product; and 2) carrying out water removal treatment on the bis (fluorosulfonyl) imide alkali metal salt crude product and a water removal agent in a good solvent of the bis (fluorosulfonyl) imide alkali metal salt, and removing the water removal agent to obtain the liquid bis (fluorosulfonyl) imide alkali metal salt. According to the present invention, the water removal treatment is performed by adding the sodium polyacrylate resin and the MOF material with the organic ligand being the benzene ring-containing carboxylic acid ligand to the bis (fluorosulfonyl) imide alkali metal salt crude product solution as the water removal agent, such that the water content in the liquid bis (fluorosulfonyl) imide alkali metal salt is reduced to less than 15 ppm, the water removal operation is simple, and the impurity ions are not introduced;

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a preparation method of liquid bifluorosulfonylimide alkali metal salt. BACKGROUND

[0002] Lithium ion batteries have been widely used due to their high energy density and high working voltage. As a potential alternative to lithium ion batteries, sodium ion batteries have attracted widespread attention in recent years due to their unique resource advantages and performance characteristics. The main advantages of sodium ion batteries are as follows: ① sodium resources are abundant and low in cost; ② higher safety; ③ more environmentally friendly; ④ better high and low temperature performance; ⑤ better fast charging performance and cycle life.

[0003] The electrolyte salt used in the secondary battery includes bifluorosulfonylimide alkali metal salt, which has high ionization and good conductivity, and can be used in the electrolyte of the secondary battery. It also maintains good compatibility with positive and negative electrode materials, which can significantly improve the high and low temperature performance of the secondary battery. Therefore, bifluorosulfonylimide lithium has very important application prospects and value.

[0004] Most of the existing synthesis methods of bifluorosulfonylimide alkali metal salt, such as lithium bifluorosulfonylimide, are to first prepare bifluorosulfonylimide, and then react with lithium carbonate or lithium hydroxide to obtain lithium bifluorosulfonylimide. However, this reaction process will generate by-products such as water, and lithium bifluorosulfonylimide is easily hygroscopic, and even can complex with water, so that the final bifluorosulfonylimide product often contains water, and the F - 、SO4 2- content exceeds the standard due to hydrolysis, which makes the product not meet the battery application standard.

[0005] At present, the more common water removal method is thionyl chloride water removal method. This method will generate a large amount of hydrogen chloride and sulfur dioxide waste gas after water removal, and will cause the chlorine ion content in the salt to be too high, which needs to consider the exhaust and re-chlorination. The water removal step is complex and easy to introduce impurities. The Chinese patent application with the application publication number CN116354319A published on June 30, 2023 discloses a preparation method of bifluorosulfonylimide salt, which is to react bifluorosulfonylimide acid with alkali metal source in a poor solvent to generate bifluorosulfonylimide salt. According to the type and amount of alkali metal source, carbonates are added to the system after reaction and carbon dioxide is introduced, or carbon dioxide is directly introduced, so that water generates bicarbonate for subsequent removal. However, the above water removal methods are relatively complex. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of liquid bifluorosulfonylimide alkali metal salt, which solves the problems of complex water removal operation and introduction of impurities during water removal in the existing preparation of liquid bifluorosulfonylimide alkali metal salt.

[0007] To solve the above technical problems, the technical scheme of the preparation method of the liquid bifluorosulfonylimide alkali metal salt of the present application is:

[0008] A preparation method of a liquid bifluorosulfonylimide alkali metal salt, comprising the following steps:

[0009] 1) reacting bifluorosulfonylimide with an alkali metal source in a poor solvent of the bifluorosulfonylimide alkali metal salt to obtain a bifluorosulfonylimide alkali metal salt crude product through a first solid-liquid separation; the alkali metal source is selected from one or more of alkali metal carbonates, alkali metal bicarbonates and alkali metal hydroxides;

[0010] 2) treating the bifluorosulfonylimide alkali metal salt crude product with a water removal agent in a good solvent of the bifluorosulfonylimide alkali metal salt to remove the water removal agent to obtain a liquid bifluorosulfonylimide alkali metal salt; the water removal agent is selected from one or both of polyacrylic acid sodium resin and MOF material; the organic ligand of the MOF material is a carboxylic acid ligand containing a benzene ring.

[0011] The present application is an improvement on the prior art, and provides a preparation method of a liquid bifluorosulfonylimide alkali metal salt, which utilizes the reaction of bifluorosulfonylimide with an alkali metal source in a poor solvent to obtain a solid bifluorosulfonylimide alkali metal salt crude product, and then reacts the bifluorosulfonylimide alkali metal salt crude product with a water removal agent in a good solvent to remove water, utilizing the adsorption capacity of polyacrylic acid sodium water-absorbing resin and MOF material with an organic ligand being a carboxylic acid ligand containing a benzene ring, to greatly reduce the water content in the liquid bifluorosulfonylimide alkali metal salt, with the water content being ≤15 ppm, and without introducing other impurity ions, with the metal ions being within 1 ppm, the chloride ion content being within 1.2 ppm, the fluoride ion content being within 12 ppm, the sulfate ion content being within 3.2 ppm, the NH2SO3 content being within 31 ppm, and the solution color being less than 11 Hazen. The preparation method of the liquid bifluorosulfonylimide alkali metal salt of the present application has simple water removal operation, and no other impurity ions are left, without the need for complex post-treatment, and is suitable for large-scale production; and the good solvent type can be selected according to the solvent type of the required electrolyte, for adaptive adjustment, which is simple and efficient.

[0012] To further improve the water removal efficiency, preferably, the mass ratio of the bifluorosulfonylimide alkali metal salt crude product to the water removal agent is 100:(0.1-0.4).

[0013] To further improve the water removal efficiency, preferably, the MOF material is selected from one or more of UiO-66, MIL-53 and MIL-125.

[0014] To further reduce the moisture content of the liquid bifluorosulfonylimide alkali metal salt, preferably, when the MOF material is selected from two of UiO-66, MIL-53 and MIL-125, the mass ratio of any two is (1-1.2):(1-1.2). When the MOF material is composed of MIL-53 and MIL-125, the mass ratio of MIL-53 and MIL-125 is (1-1.2):(1-1.2). When the MOF material is composed of UiO-66 and MIL-125, the mass ratio of UiO-66 and MIL-125 is (1-1.2):(1-1.2).

[0015] To further remove water from the crude bifluorosulfonylimide alkali metal salt, preferably, when the water removal agent is a sodium polyacrylate resin, the mass ratio of the crude bifluorosulfonylimide alkali metal salt to the water removal agent is 100:(0.3-0.4); and the weight average molecular weight of the sodium polyacrylate resin is 3000000-7000000.

[0016] To further remove water from the crude bifluorosulfonylimide alkali metal salt, preferably, when the water removal agent is a MOF material, the mass ratio of the crude bifluorosulfonylimide alkali metal salt to the water removal agent is 100:(0.1-0.2).

[0017] To further improve the water removal efficiency and avoid lithium loss, preferably, the temperature of the water removal treatment is 5-25℃, and the time of the water removal treatment is 2-10h.

[0018] To further improve the contact between the crude bifluorosulfonylimide alkali metal salt and the water removal agent, preferably, for every 100g of the crude bifluorosulfonylimide alkali metal salt, the corresponding amount of the good solvent added is (235-240)g.

[0019] To further reduce the moisture content of the liquid bifluorosulfonylimide alkali metal salt, preferably, after the first solid-liquid separation in step 1), the crude bifluorosulfonylimide alkali metal salt is subjected to beating treatment in a poor solvent, and then subjected to nitrogen blowing after the second solid-liquid separation. The beating treatment can further separate the moisture in the solid crude bifluorosulfonylimide alkali metal salt, and the nitrogen blowing can remove the residual moisture on the surface of the crude bifluorosulfonylimide alkali metal salt.

[0020] To further reduce the moisture content of the liquid bifluorosulfonylimide alkali metal salt, preferably, the beating treatment is performed 2-3 times, and the nitrogen blowing is performed for 12-48h. DETAILED DESCRIPTION

[0021] The technical concept of the preparation method of the liquid bifluorosulfonylimide alkali metal salt provided by the present application is as follows:

[0022] The existing double fluorosulfonylimide alkali metal salt preparation process introduces other impurity ions or needs very complex processing steps. The present application adds polyacrylic acid sodium resin, an organic ligand, and a MOF material containing a benzene ring carboxylic acid ligand as a water removal agent to the double fluorosulfonylimide alkali metal salt crude product solution for water removal treatment, which can reduce the water content in the liquid double fluorosulfonylimide alkali metal salt to below 15 ppm, without introducing impurity ions, and with less influence on the color of the liquid salt.

[0023] The present application provides a liquid double fluorosulfonylimide alkali metal salt preparation method, which comprises the following steps:

[0024] 1) reacting double fluorosulfonylimide with an alkali metal source in a poor solvent of double fluorosulfonylimide alkali metal salt to obtain double fluorosulfonylimide alkali metal salt crude product through first solid-liquid separation; the alkali metal source is selected from one or more of alkali metal carbonate, alkali metal bicarbonate and alkali metal hydroxide; the double fluorosulfonylimide alkali metal salt crude product is beaten in the poor solvent for 2-3 times, and then subjected to nitrogen blowing for 12-48 h after second solid-liquid separation.

[0025] When the alkali metal source is alkali metal carbonate, the molar ratio of double fluorosulfonylimide to alkali metal carbonate is (1.7-2):1; when the alkali metal source is alkali metal bicarbonate, the molar ratio of double fluorosulfonylimide to alkali metal bicarbonate is (0.8-1.4):1. The reaction involves the following equation:

[0026] 2HN(SO2F)2+M2CO3=2MN(SO2F)2+H2O+CO2↑;

[0027] HN(SO2F)2+MHCO3=MN(SO2F)2+H2O+CO2↑; wherein M is an alkali metal.

[0028] When the alkali metal source is alkali metal hydroxide, the reaction equation is as follows:

[0029] HN(SO2F)2+M(OH)=MN(SO2F)2+H2O; wherein M is an alkali metal.

[0030] The poor solvent in step 1) is selected from one or more of dichloromethane, 1,2-dichloroethane, n-hexane, and carbon tetrachloride. The amount of poor solvent added is 4-12 times the mass of double fluorosulfonylimide.

[0031] The reaction in step 1) is carried out by adding difluorosulfurylimide dropwise in a solution of a source of alkali metal and a poor solvent at 0-3°C. The reaction temperature is 5-30°C, and the reaction time is 1-8h. More preferably, the reaction time is 5-8h. It can be understood that the reaction time refers to the time after the completion of the dropwise addition of difluorosulfurylimide at 0-3°C.

[0032] The first solid-liquid separation in step 1) is filtration, and the second solid-liquid separation is positive pressure filtration.

[0033] It can be understood that the poor solvent used in the beating treatment can be different from the poor solvent used in the reaction. For example, one poor solvent is used in the beating treatment, and another poor solvent is used in the reaction; or two poor solvents are used in the beating treatment, and one of the two poor solvents is used in the reaction. After each beating treatment, a second solid-liquid separation is performed, and the solid obtained after each second solid-liquid separation can be subjected to nitrogen blowing, or nitrogen blowing is performed after the last second solid-liquid separation.

[0034] The alkali metal salt of difluorosulfurylimide in step 1) is sodium difluorosulfurylimide or potassium difluorosulfurylimide.

[0035] 2) The crude alkali metal salt of difluorosulfurylimide is subjected to water removal treatment with a water removal agent in a good solvent of the alkali metal salt of difluorosulfurylimide, and the liquid alkali metal salt of difluorosulfurylimide is obtained after removing the water removal agent; the water removal agent is selected from one or both of a sodium polyacrylate resin (CAS: 9003-04-7, M w = 3000000-7000000) and a MOF material; the organic ligand of the MOF material is a carboxylic acid ligand containing a benzene ring.

[0036] The mass ratio of the crude alkali metal salt of difluorosulfurylimide to the water removal agent is 100:(0.1-0.4). When the water removal agent is a sodium polyacrylate resin, the mass ratio of the crude alkali metal salt of difluorosulfurylimide to the water removal agent is 100:(0.3-0.4); when the water removal agent is a MOF material, the mass ratio of the crude alkali metal salt of difluorosulfurylimide to the water removal agent is 100:(0.1-0.2).

[0037] The MOF material in step 2) is selected from one or more of 1,4-dicarboxybenzene zirconium (UiO-66, CAS: 1072413-89-8), aluminum terephthalate (MIL-53(Al), CAS: 654061-20-8), and MIL-125(Ti) (CAS: 1193372-03-0).

[0038] The mass ratio of any two of the MOF materials in step 2) is (1-1.2):(1-1.2). When the MOF materials consist of MIL-53 and MIL-125, the mass ratio of MIL-53 and MIL-125 is (1-1.2):(1-1.2). When the MOF materials consist of UiO-66 and MIL-125, the mass ratio of UiO-66 and MIL-125 is (1-1.2):(1-1.2).

[0039] The temperature of the water removal treatment in step 2) is 5-25℃, and the time of the water removal treatment is 2-10h. The removal of the water removal agent is achieved by filtration.

[0040] It should be noted that the amount of the good solvent added is calculated according to the mass concentration of the liquid bifluorosulfonylimide alkali metal salt being 30±0.5%, and for every 100g of the crude bifluorosulfonylimide alkali metal salt, the mass of the good solvent added is (235-240)g.

[0041] It can be understood that the good solvent is selected according to the solvents commonly used for electrolyte solutions, and the good solvent is selected from one or more of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, and propylene carbonate. When the good solvent includes diethyl carbonate and ethylene carbonate, the mass ratio of diethyl carbonate and ethylene carbonate is (160-170):(70-75).

[0042] The embodiments of the present application will be further described below in conjunction with specific examples. The chemical reagents involved in the following examples, unless otherwise specified, are all commercially available conventional goods.

[0043] I. Specific examples of the method for preparing the liquid bifluorosulfonylimide alkali metal salt of the present application

[0044] Example 1

[0045] The method for preparing the sodium bifluorosulfonylimide liquid salt of the present example is as follows:

[0046] 1) 1448g of dichloromethane (4 times the mass of the bifluorosulfonylimide), 106g of sodium carbonate were sequentially added to a reaction vessel, placed in a 0℃ constant temperature freezing bath and stirred until the solids were fully dispersed in the solvent, then 362g of bifluorosulfonylimide was slowly added dropwise, after the addition was completed, the temperature was raised to 10℃ and reacted for 5h, after the reaction was completed, the sodium bifluorosulfonylimide solid crude salt was obtained by filtration, and dichloromethane was added for beating 2-3 times, specifically: after each beating was completed, the filter cake was taken out and beaten again, and the process was repeated 2-3 times, and the filter cake of the last beating was subjected to positive pressure purging with nitrogen for 12h, finally 399.95g of sodium bifluorosulfonylimide crude salt was obtained, with a yield of 98.51%.

[0047] 2) Take 500 ml flask, add 235 g dimethyl carbonate into 0 °C constant temperature refrigeration bath, take the double fluorosulfonyl imide sodium coarse salt 100 g obtained in step 1) slowly add into the flask, stir to dissolve completely, stop stirring, add 0.335 g sodium polyacrylate resin, the temperature rises to 25 °C, fully react for 2 h, filter the insoluble in the liquid salt to obtain double fluorosulfonyl imide sodium liquid salt.

[0048] Example 2

[0049] The preparation method of double fluorosulfonyl imide sodium liquid salt in this example is as follows:

[0050] 1) Add 1,2-dichloroethane 4344 g (12 times the mass of double fluorosulfonyl imide), 95.4 g sodium carbonate into the reaction container in turn, place in 0 °C constant temperature refrigeration bath and stir until the solids are fully dispersed in the solvent, then slowly add 362 g double fluorosulfonyl imide, after the addition is completed, the temperature is raised to 5 °C and reacted for 6 h, after the reaction is completed, filter and add 1,2-dichloroethane for beating 2-3 times, after each beating is completed, carry out positive pressure filtration, the filter cake after the last beating and filtration is subjected to positive pressure blowing with nitrogen for 48 h, finally 356.41 g double fluorosulfonyl imide sodium coarse salt is obtained, with a yield of 97.54%.

[0051] 2) Take 500 ml flask, add 236 g dimethyl carbonate into 0 °C constant temperature refrigeration bath, take the double fluorosulfonyl imide sodium coarse salt 100 g obtained in step 1) slowly add into the flask, stir to dissolve completely, stop stirring, add 0.1008 g UiO-66, the temperature rises to 25 °C, fully react for 2 h, filter the insoluble in the liquid salt to obtain double fluorosulfonyl imide sodium liquid salt.

[0052] Example 3

[0053] The preparation method of double fluorosulfonyl imide sodium liquid salt in this example is as follows:

[0054] 1) Add n-hexane 2164 g (8 times the mass of double fluorosulfonyl imide), 126 g sodium bicarbonate into the reaction container in turn, place in 0 °C constant temperature refrigeration bath and stir until the solids are fully dispersed in the solvent, then slowly add 270.5 g double fluorosulfonyl imide, after the addition is completed, react for 8 h, after the reaction is completed, filter and add n-hexane for beating 2-3 times, after each beating is completed, carry out positive pressure filtration, the filter cake after the last beating and filtration is subjected to positive pressure blowing with nitrogen for 36 h, finally 295.76 g double fluorosulfonyl imide sodium coarse salt is obtained, with a yield of 97.13%.

[0055] 2) Take 500 ml flask, add 165.2 g of diethyl carbonate and 70.8 g of ethylene carbonate into 0 °C constant temperature refrigeration bath, take 100 g of crude salt of sodium bisfluorosulfonylimide obtained in step 1) and slowly add it into the flask, stir to dissolve completely, stop stirring after complete dissolution, add 0.1344 g of MIL-53, and the temperature is raised to 5 °C, and react for 10 h, filter the insoluble matter in the liquid salt to obtain the liquid salt of sodium bisfluorosulfonylimide.

[0056] Example 4

[0057] The preparation method of the liquid salt of sodium bisfluorosulfonylimide of the present example is as follows:

[0058] 1) Add carbon tetrachloride 3620 g (10 times the mass of bisfluorosulfonylimide), 169.7 g of sodium bicarbonate into the reaction container in turn, place in 0 °C constant temperature refrigeration bath and stir until the solids are fully dispersed in the solvent, then slowly add 362 g of bisfluorosulfonylimide, after the addition is completed, the temperature is raised to 15 °C and reacted for 4 h, after the reaction is completed, filter and add carbon tetrachloride for beating 2-3 times, after each beating is completed, carry out positive pressure filtration, the filter cake of the last beating and filtration is subjected to positive pressure blowing with nitrogen for 42 h, finally 392.15 g of crude salt of sodium bisfluorosulfonylimide is obtained, with a yield of 96.59%.

[0059] 2) Take 500 ml flask, add 118 g of dimethyl carbonate and 118 g of ethylene carbonate into 0 °C constant temperature refrigeration bath, take 100 g of crude salt of sodium bisfluorosulfonylimide obtained in step 1) and slowly add it into the flask, stir to dissolve completely, stop stirring after complete dissolution, add 0.1008 g of MIL-125, and the temperature is raised to 15 °C, and react for 5 h, filter the insoluble matter in the liquid salt to obtain the liquid salt of sodium bisfluorosulfonylimide.

[0060] Example 5

[0061] The preparation method of the liquid salt of sodium bisfluorosulfonylimide of the present example is as follows:

[0062] 1) Add dichloroethane 1810 g (5 times the mass of bisfluorosulfonylimide), 106 g of sodium carbonate into the reaction container in turn, place in 0 °C constant temperature refrigeration bath and stir until the solids are fully dispersed in the solvent, then slowly add 362 g of bisfluorosulfonylimide, after the addition is completed, the temperature is raised to 30 °C and reacted for 2 h, after the reaction is completed, filter and add a mixed solvent of dichloromethane and dichloroethane for beating 2-3 times, after each beating is completed, carry out positive pressure filtration, the filter cake of the last beating and filtration is subjected to positive pressure blowing with nitrogen for 24 h, finally 398.73 g of crude salt of sodium bisfluorosulfonylimide is obtained, with a yield of 98.21%.

[0063] 2) Take 500ml flask, add 238g propylene carbonate into 0°C constant temperature refrigeration bath, take the crude salt of sodium bisfluorosulfonylimide 100g from step 1) and slowly add it into the flask, stir to dissolve completely, stop stirring after complete dissolution, add 0.0672g MIL-53 and 0.0672g MIL-125, temperature rises to 10°C, react for 8h, filter the insoluble in the liquid salt to obtain the liquid salt of sodium bisfluorosulfonylimide.

[0064] Example 6

[0065] The preparation method of the liquid salt of sodium bisfluorosulfonylimide of the present example is as follows:

[0066] 1) Add dichloroethane 3620g (10 times the mass of bisfluorosulfonylimide), 112.22g potassium hydroxide into the reaction container in turn, place in 0°C constant temperature refrigeration bath and stir until the solid is fully dispersed in the solvent, then slowly add 362g bisfluorosulfonylimide, after the addition is completed, the temperature is raised to 30°C and reacted for 2h, after the reaction is completed, filter and add dichloromethane and dichloroethane mixed solvent to beat for 2-3 times, after each beating is completed, carry out positive pressure filtration, the filter cake of the last beating and filtration is subjected to positive pressure blowing with nitrogen for 24h, finally 423.89g of crude potassium bisfluorosulfonylimide is obtained, with a yield of 96.73%.

[0067] 2) Take 500ml flask, add 238g propylene carbonate into 0°C constant temperature refrigeration bath, take the crude salt of potassium bisfluorosulfonylimide 100g from step 1) and slowly add it into the flask, stir to dissolve completely, stop stirring after complete dissolution, add 0.1014g MIL-53, temperature rises to 8°C, react for 8h, filter the insoluble in the liquid salt to obtain the liquid salt of potassium bisfluorosulfonylimide.

[0068] Example 7

[0069] The preparation method of the liquid salt of sodium bisfluorosulfonylimide of the present example is as follows:

[0070] 1) Add dichloroethane 3620g (10 times the mass of bisfluorosulfonylimide), 112.22g potassium hydroxide into the reaction container in turn, place in 0°C constant temperature refrigeration bath and stir until the solid is fully dispersed in the solvent, then slowly add 362g bisfluorosulfonylimide, after the addition is completed, the temperature is raised to 30°C and reacted for 2h, after the reaction is completed, filter and add dichloromethane and dichloroethane mixed solvent to beat for 2-3 times, after each beating is completed, carry out positive pressure filtration, the filter cake of the last beating and filtration is subjected to positive pressure blowing with nitrogen for 24h, finally 423.89g of crude potassium bisfluorosulfonylimide is obtained, with a yield of 96.73%.

[0071] 2) Take 500ml flask, add 238g methyl ethyl carbonate into 0°C constant temperature refrigeration bath, take the sodium bisfluorosulfonylimide coarse salt 100g from step 1) slowly add into the flask, stir to dissolve completely, stop stirring after complete dissolution, add 0.0676g UiO-66 and 0.0672g MIL-125, temperature rises to 20°C, fully react for 6h, filter the insoluble in the liquid salt to obtain the sodium bisfluorosulfonylimide liquid salt.

[0072] Example 2

[0073] Example 2

[0074] The preparation method of the sodium bisfluorosulfonylimide liquid salt of the present comparative example is basically the same as that of Example 1, except that step 2): take 500ml flask, add 236g methyl ethyl carbonate into 0°C constant temperature refrigeration bath, take the sodium bisfluorosulfonylimide coarse salt 100g from step 1) slowly add into the flask, stir to dissolve completely, filter to obtain the sodium bisfluorosulfonylimide liquid salt after complete dissolution.

[0075] Example 2

[0076] The preparation method of the sodium bisfluorosulfonylimide liquid salt of the present comparative example is basically the same as that of Example 2, except that step 2): take 500ml flask, add 236g methyl ethyl carbonate into 0°C constant temperature refrigeration bath, take the sodium bisfluorosulfonylimide coarse salt 100g from step 1) slowly add into the flask, stir to dissolve completely, filter to obtain the sodium bisfluorosulfonylimide liquid salt after complete dissolution.

[0077] Example 2

[0078] The preparation method of the sodium bisfluorosulfonylimide liquid salt of the present comparative example is basically the same as that of Example 3, except that step 2): take 500ml flask, add 165.2g diethyl carbonate and 70.8g ethylene carbonate into 0°C constant temperature refrigeration bath, take the sodium bisfluorosulfonylimide coarse salt 100g from step 1) slowly add into the flask, stir to dissolve completely, filter to obtain the sodium bisfluorosulfonylimide liquid salt after complete dissolution.

[0079] Example 2

[0080] The preparation method of the sodium bisfluorosulfonylimide liquid salt of the present comparative example is basically the same as that of Example 4, except that step 2): take 500ml flask, add 118g dimethyl carbonate and 118g ethylene carbonate into 0°C constant temperature refrigeration bath, take the sodium bisfluorosulfonylimide coarse salt 100g from step 1) slowly add into the flask, stir to dissolve completely, filter to obtain the sodium bisfluorosulfonylimide liquid salt after complete dissolution.

[0081] Example 2

[0082] The preparation method of the sodium liquid salt of bisfluorosulfone imide of the present comparative example is basically the same as that of Example 5, except that in step 2), 238 g of propylene carbonate is added into a 500 ml flask and placed in a 0°C constant temperature freezing bath, and 100 g of the crude sodium salt of bisfluorosulfone imide obtained in step 1) is slowly added into the flask, and stirred to dissolve completely, and then filtered to obtain the sodium liquid salt of bisfluorosulfone imide.

[0083] Comparative Example 6

[0084] The preparation method of the potassium liquid salt of bisfluorosulfone imide of the present comparative example is basically the same as that of Example 6, except that in step 2), 238 g of propylene carbonate is added into a 500 ml flask and placed in a 0°C constant temperature freezing bath, and 100 g of the crude potassium salt of bisfluorosulfone imide obtained in step 1) is slowly added into the flask, and stirred to dissolve completely, and then filtered to obtain the potassium liquid salt of bisfluorosulfone imide.

[0085] Comparative Example 7

[0086] The preparation method of the sodium liquid salt of bisfluorosulfone imide of the present comparative example is basically the same as that of Example 7, except that in step 2), 238 g of methyl ethyl carbonate is added into a 500 ml flask and placed in a 0°C constant temperature freezing bath, and 100 g of the crude sodium salt of bisfluorosulfone imide obtained in step 1) is slowly added into the flask, and stirred to dissolve completely, and then filtered to obtain the sodium liquid salt of bisfluorosulfone imide.

[0087] III. Experimental Examples

[0088] The anion content (including chloride ion, fluoride ion, sulfate ion, sulfamate ion) in the liquid alkali metal salt of bisfluorosulfone imide of the examples and comparative examples is tested by ion chromatography; the metal ion content in the liquid alkali metal salt of bisfluorosulfone imide is tested by ICP-OES / MS; the water content in the liquid alkali metal salt of bisfluorosulfone imide is tested by Karl Fischer method; and the colority of the liquid alkali metal salt of bisfluorosulfone imide is tested by platinum-cobalt colorimetry.

[0089] The anion content in the liquid alkali metal salt of bisfluorosulfone imide of the examples and comparative examples is shown in Table 1.

[0090] Table 1 Test results of anion content in the liquid alkali metal salt of bisfluorosulfone imide

[0091]

[0092] The metal ion content in the liquid alkali metal salt of bisfluorosulfone imide of the examples and comparative examples is shown in Table 2.

[0093] Table 2 Test results of metal ion content in the liquid alkali metal salt of bisfluorosulfone imide

[0094]

[0095] The moisture content and colority of the liquid bifluorosulfonylimide alkali metal salt of the examples and comparative examples are shown in Table 3.

[0096] Table 3 Test results of moisture content and colority of liquid bifluorosulfonylimide alkali metal salt

[0097]

[0098]

[0099] “-” means not tested.

[0100] According to the examples, in the case of not excluding part of the mass loss in the operation process, the yield of the bifluorosulfonylimide sodium / potassium solid crude salt is all above 96%. As can be seen from Tables 1-3, compared with not introducing sodium polyacrylate resin and metal organic framework MOF material for water removal operation, the moisture content of the bifluorosulfonylimide sodium / potassium liquid salt obtained by the present application is greatly reduced, and the moisture content is ≤15 ppm. And no impurity ions are introduced, the test results of metal ions are all within 1 ppm, the content of chloride ions is within 1.2 ppm, the content of fluoride ions is within 12 ppm, the content of sulfate ions is within 3.2 ppm, the content of NH2SO3 - is within 31 ppm, and the solution colority is less than 11 Hazen.

[0101] Compared with molecular sieves, the use amount of the sodium polyacrylate resin and the metal organic framework MOF material used in the present application is lower, and the effect on the filtration speed in mass production is smaller (the negative effect of less insoluble substances on membrane hole blockage is smaller), and the effect on ton-level or higher output is relatively obvious. The specific surface area of the molecular sieve powder is larger, and the use of a large amount in membrane filtration or circulating filtration can easily cause blockage phenomenon.

[0102] Finally, it should be noted that: the above only describes the preferred embodiments of the present application, and is not used to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the preparation of a liquid bifluorosulfonylimide alkali metal salt, characterized in that, The method comprises the following steps: 1) reacting difluorosulfurylimide with an alkali metal source in a poor solvent of an alkali metal salt of difluorosulfurylimide to obtain a crude alkali metal salt of difluorosulfurylimide through first solid-liquid separation; the alkali metal source is selected from one or more of alkali metal carbonates, alkali metal bicarbonates and alkali metal hydroxides; 2) performing water removal treatment on the crude alkali metal salt of difluorosulfurylimide with a water removal agent in a good solvent of the alkali metal salt of difluorosulfurylimide, and obtaining liquid alkali metal salt of difluorosulfurylimide after removing the water removal agent; the water removal agent is selected from one or both of a sodium polyacrylate resin and a MOF material; the organic ligand of the MOF material is a carboxylic acid ligand containing a benzene ring.

2. The process for preparing a liquid bifluorosulfonylimide alkali metal salt according to claim 1, characterized by, The mass ratio of the crude alkali metal salt of difluorosulfurylimide to the water removal agent is 100: (0.1-0.4).

3. The method for preparing liquid bis(fluorosulfonyl)imide alkali metal salt as described in claim 1, characterized in that, The MOF material is selected from one or more of UiO-66, MIL-53 and MIL-125.

4. The method for producing a liquid bifluorosulfonylimide alkali metal salt according to claim 3, characterized by, When the MOF material is selected from two of UiO-66, MIL-53 and MIL-125, the mass ratio of any two is (1-1.2):(1-1.2).

5. The process for the preparation of liquid bifluorosulfonylimide alkali metal salt according to any one of claims 1 to 4, characterized in that, When the water removal agent is a sodium polyacrylate resin, the mass ratio of the crude alkali metal salt of difluorosulfurylimide to the water removal agent is 100: (0.3-0.4); the weight average molecular weight of the sodium polyacrylate resin is 3,000,000-7,000,000.

6. The process for the preparation of liquid bifluorosulfonylimide alkali metal salt according to any one of claims 1 to 4, characterized in that, When the water removal agent is a MOF material, the mass ratio of the crude alkali metal salt of difluorosulfurylimide to the water removal agent is 100: (0.1-0.2).

7. The method for preparing liquid bis(fluorosulfonyl)imide alkali metal salt as described in claim 1, characterized in that, The temperature of the water removal treatment is 5-25°C, and the time of the water removal treatment is 2-10h.

8. The method for preparing liquid bis(fluorosulfonyl)imide alkali metal salt as described in claim 1, characterized in that, The mass of the good solvent corresponding to 100g of the crude alkali metal salt of difluorosulfurylimide is (235-240)g.

9. The method for preparing liquid bis(fluorosulfonyl)imide alkali metal salt as described in claim 1, characterized in that, After the first solid-liquid separation in step 1), the crude alkali metal salt of difluorosulfurylimide is subjected to beating treatment in a poor solvent, and then subjected to second solid-liquid separation and nitrogen blowing.

10. The method for preparing the liquid bis(fluorosulfonyl)imide alkali metal salt as described in claim 9, characterized in that, The beating treatment is performed for 2-3 times, and the nitrogen blowing is performed for 12-48h.

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